Tank-type toilet installations are, of course, widely used, particularly for residential installations. At the present time most such toilets have flushing systems comprised of a float controlled water supply valve, an overflow pipe, a large ball-type flush valve and an actuating lever for lifting the ball valve off its seat to initiate the flushing cycle. Such flushing systems normally operate satisfactorily, but have some disadvantages. For example, most homeowners are aware that if the float controlled water supply valve fails to close satisfactorily the water continues to run, overfilling the tank and leaving by the overflow pipe thereby resulting in a substantial waste of water. Furthermore, the float controlled water supply valve which depends upon the water level in the tank to remain closed is also ineffective in preventing the property damage that can result in the event the water tank cracks or springs a leak. Still further, the float controlled water supply valve is subject to opening by the "water hammer effect" which also can result in a substantial waste of water.
The large ball-type flush valve employed in most residential toilet tank installations also has its disadvantages. The ball-type flush valve many times fails to seat properly causing leakage of tank water into the water closet bowl and a waste of water. In addition, many of the malfunctions that occur with the conventional residential tank flushing systems are due to the mechanical linkages between the ball-type flush valve and the actuating lever which raises the ball from its valve seat and permits the flushing cycle to be initiated. As a result, the components of the conventional toilet tank flushing system must be precisely aligned when installed in a tank.
The disadvantages of conventional ball-type flush valves are overcome by siphon-type valves such as that shown in copending U.S. application Ser. No. 642,948, filed Dec. 22, 1975; now Pat. No. 4,024,589but siphon valves require some reliable means to initiate the siphon action and the disadvantages of the float control remain. All of the noted problems may be cured by doing away with the tank entirely and using a flushometer-type valve to deliver a predetermined quantity of flush water; but this arrangement is generally unsuitable for residential use or any other situation where there is inadequate water supply.
A control valve which operates independent of the tank water level and is particularly adapted for use in a flushing system employing a siphon flush valve is disclosed in the copending application of Peter M. Milnes, Ser. No. 700,912 filed June 29, 1976 for "Valve Controlled Flushing System," now U.S. Pat. No. 4,034,423.
The aforementioned control valve utilizes a pressure biased piston which is ordinarily seated against the water supply by supply line pressure which is transferred by a bypass circuit to a timing pressure chamber behind and exposed to the rear face of the piston. Located in the bypass circuit between the supply pressure and the timing pressure chamber is an actuating valve which ordinarily allows the free flow of line pressure, but which can be triggered to block the transfer of supply line pressure and relieve the pressure on the rear face of the piston thus allowing the piston to be moved by supply line pressure from a closed to an open position and allowing the flow of supply water into the toilet tank. The control valve, because it utilizes water supply line pressure to remain closed, is independent of the water level in the tank, and, therefore, in the event of tank leakage the water loss is restricted to that contained within the tank. This, of course, eliminates the possibility of property damage that could result from the subsequent water flow with a water level controlled valve. In addition, because the supply line pressure is utilized to maintain the piston of the control valve in a closed position, the control valve will not open due to the "water hammer effect" as will float controlled valves which depend upon the water level in the tank to hold them closed against supply line pressure.